Portion of a display screen with a user interface



FIG. 1 is a front view showing of a portion of a display screen with a user interface showing a first embodiment of the new design.

FIG. 2 is a front view showing of a portion of a display screen with a user interface showing a second embodiment of the new design; and,

FIG. 3 is a front view of a portion of a display screen with a user interface showing a third embodiment of the new design.

The broken line showing of the display screen is included for the purpose of illustrating portions of the article and forms no part of the claimed design. 

The ornamental design for a portion of a display screen with a user interface, as shown and described. 